23a. Based on genetic data, Penhallurick & Wink (2004)
proposed that Puffinus be subdivided into two genera: (1) Ardenna
for creatopus/carneipes, gravis, griseus, tenuirostris,
pacifica, and bulleri; and (2) Puffinus for all other
taxa. However, see Rheindt & Austin (2005) on use of genetic distances for
assigning taxon rank.SACC proposal to
split Ardenna from Puffinus did not pass.Other genetic data (Austin et al. 2004, Pyle et al. 2011) have
confirmed these findings, and Dickinson
& Remsen (2013) and del Hoyo & Collar (2014) adopted this
classification.Proposal badly needed.

Note that we previously rejected a
proposal to do this based on Penhallurick &
Wink (2004), who found a deep split within Puffinus.Objections were that this was based on only 1
gene, and that the two proposed genera were diagnosed mainly by body size.However, Jaramillo, who knows these pelagics
better than anyone else on SACC, pointed out biogeographic themes that
separated the two genera.

New information:Shortly after
publication of the Penhallurick-Wink paper, Austin et al. (2004) published a
phylogeny, also based exclusively on cytochrome b.Not surprisingly, therefore, they also found
the same two divisions in Puffinus.Both studies found that Calonectris was the most closely related genus to Puffinus but were unable to resolve
relationships among Calonectris and
the two groups of Puffinus.

Pyle
et al. (2011) also used cytochrome b to produce a phylogeny of shearwaters (the
focus of which was to investigate the specimen that they showed was a separate
species, Puffinus bryani), and their
tree was, no surprise, similar to the previous two.Calonectris
is sister to true Puffinus, but the
support for that node is weak.

Analysis and recommendation:If the support for
a Calonectris-Puffinus sensu stricto were solid, then there would be no
controversy in recognizing Ardenna as
separate from Puffinus.As it stands, the decision is
subjective.The three published trees
are all based on the same mitochondrial gene.Nonetheless, I favor a YES on this one – we adopted the split in
Dickinson & Remsen (2013), and HBW also did this independently.Our rationale was that the degree of genetic
divergence, at least in cyt b, is fairly deep, and regardless of sister
relationships, if we recognized Calonectris,
then we also ought to recognize Ardenna
as an equally divergent group.As noted
long ago by Alvaro, the two groups of shearwaters differ in general
biogeography.Except for Wedge-tailed (pacifica), the Ardenna shearwaters (Buller’s bulleri,
Slender-billed tenuirostris, Sooty grisea, Great gravis, Pale-footed carneipes,
Pink-footed creatopus) breed in
cold-water islands in the Southern Hemisphere, mainly in the Pacific), whereas Puffinus shearwaters are more
widespread, especially at tropical latitudes, and several species breed in the
Atlantic and Mediterranean (e.g. Manx puffinus
and Audubon’s lherminieri).True Puffinus
are largely black or dark brownish above and white below, whereas species in
the Ardenna group show much greater
variation in plumage (and none are truly solid blackish above).These are all weak differences, with overlap.(I predict that seabird biologists will find
stronger, non-overlapping differences.)

Nonetheless,
Peters (1931) recognized the two groups as subgenera, but placed Wedge-tailed
in its own subgenus Thyellodroma.Oberholser (1917; https://sora.unm.edu/sites/default/files/journals/auk/v034n04/p0471-p0475.pdf)
evaluated all the shearwaters on morphological grounds, including the four
genera mentioned above plus Hemipuffinus (for
carneipes and creatopus), Alphapuffinus
(for assimilis, lherminieri, persicus),
and Neonectris (for tenuirostris and griseus).He concluded that Calonectris, Ardenna, Thyellodroma,
and Puffinus should all be recognized
based on morphological differences (but not the other three genera).This classification would match that in the
proposal and in the classification of Penhallurick and Wink except for
inclusion of Thyellodroma in Ardenna.Oberholser’s Thyellodroma does
form a monophyletic group (pacifica
and bulleri) that is sister to the
rest of Ardenna (and might be the
topic of some future proposal if a new phylogeny emerges with many additional
loci that would allow a broader view of degrees of divergence).

A
YES vote, to recognize Ardenna, would
produce the follow changes in our classification.Let’s call this subproposal A.

Note
the changes to the variable endings of A.
pacifica and A. grisea.

A
minor bookkeeping change in linear sequence is needed regardless of the vote on
A.Let’s call this subproposal B.Following the convention of linear sequencing
in which the least diverse branch is listed first, the sequence should be
(using the topology in Pyle et al., in which all the nodes have reasonable
support), with indentations used to signal nodes:

pacifica

bulleri

tenuirostris

grisea

gravis

creatopus

carneipes

I recommend a YES on this minor
sequence change because it makes our sequence reflect the best data on
relationships.

Finally, one more extremely minor
change in our classification is needed to make our sequence conform to the
topology of the tree in Pyle et al. (2011).The reason that we ranked P.subalaris as a separate species is that Austin et al. (2004), and now Pyle et
al. (2011) found that subalaris falls outside the large group of species
that contains P. lherminieri (and P. assimilis).Therefore, following conventions of linear
sequencing, subalaris should precede P. lherminieri and P.
assimilis.Let’s call this
subproposal C, and I recommend a YES on this as a matter of bookkeeping.

Literature Cited

AUSTIN, J. J.,
V. BRETAGNOLLE, AND E. PASQUET. 2004. A global molecular phylogeny of the small
Puffinus shearwaters and implications for systematics of the
Little-Audubon Shearwater complex. Auk 121: 847-864.

Comments
from Robbins: “Given that this is totally subjective I could go either way.”

Comments from Stiles:

“A. YES.Given
that the splits between Ardenna-Puffinus and
Puffinus-Calonectris are of similar
age, it seems reasonable to recognize Ardenna,
even though only a single gene was sequenced.

“B. YES, on present evidence (although one hopes that
more of the genotypes may son be sequenced).

“C. YES, for keeping the books consistent.”

Comments from Nores:

“A: YES, although not very convinced
(among other things, only a single gene was sequenced).

“B: YES

“C: YES”

Comments
from Pacheco: “A – YES;
According to the proposal, since the three studies demonstrated the deep level
of genetic divergence, despite based only on cytochrome b

B – YES

C – YES”

Comments from Jaramillo: “A – YES. As noted in the proposal, there are
also biogeographical considerations. Also Ardenna
are bulkier, heftier birds than Puffinus.
The Thyellodroma subgenus is indeed
structurally different, with the wedge tail, and the more bowed-wing flight
style but more data is needed on them. Currently Ardenna is diverse enough between the bulkier gravis-carneipes-creatopus
group vs. grisea-tenuirostris that Thyellodroma fits ok in this relatively
diverse genus. B – YES.
C – YES,
move order of subalaris.